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<refentry>

  <refentryinfo>
    <date>Jun 30, 2000</date>
  </refentryinfo>

  <refmeta>
    <refentrytitle>lwres_gnba</refentrytitle>
    <manvolnum>3</manvolnum>
    <refmiscinfo>BIND9</refmiscinfo>
  </refmeta>

  <docinfo>
    <copyright>
      <year>2004</year>
      <year>2005</year>
      <year>2007</year>
      <holder>Internet Systems Consortium, Inc. ("ISC")</holder>
    </copyright>
    <copyright>
      <year>2000</year>
      <year>2001</year>
      <holder>Internet Software Consortium.</holder>
    </copyright>
  </docinfo>

  <refnamediv>
    <refname>lwres_gnbarequest_render</refname>
    <refname>lwres_gnbaresponse_render</refname>
    <refname>lwres_gnbarequest_parse</refname>
    <refname>lwres_gnbaresponse_parse</refname>
    <refname>lwres_gnbaresponse_free</refname>
    <refname>lwres_gnbarequest_free</refname>
    <refpurpose>lightweight resolver getnamebyaddress message handling</refpurpose>
  </refnamediv>

  <refsynopsisdiv>

    <funcsynopsis>
<funcsynopsisinfo>
#include &lt;lwres/lwres.h&gt;
</funcsynopsisinfo>

<funcprototype>
        <funcdef>
lwres_result_t
<function>lwres_gnbarequest_render</function>
</funcdef>
        <paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>
        <paramdef>lwres_gnbarequest_t *<parameter>req</parameter></paramdef>
        <paramdef>lwres_lwpacket_t *<parameter>pkt</parameter></paramdef>
        <paramdef>lwres_buffer_t *<parameter>b</parameter></paramdef>
        </funcprototype>

<funcprototype>
        <funcdef>
lwres_result_t
<function>lwres_gnbaresponse_render</function>
</funcdef>
        <paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>
        <paramdef>lwres_gnbaresponse_t *<parameter>req</parameter></paramdef>
        <paramdef>lwres_lwpacket_t *<parameter>pkt</parameter></paramdef>
        <paramdef>lwres_buffer_t *<parameter>b</parameter></paramdef>
        </funcprototype>
<funcprototype>
        <funcdef>
lwres_result_t
<function>lwres_gnbarequest_parse</function></funcdef>
        <paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>
        <paramdef>lwres_buffer_t *<parameter>b</parameter></paramdef>
        <paramdef>lwres_lwpacket_t *<parameter>pkt</parameter></paramdef>
        <paramdef>lwres_gnbarequest_t **<parameter>structp</parameter></paramdef>
        </funcprototype>
<funcprototype>
        <funcdef>
lwres_result_t
<function>lwres_gnbaresponse_parse</function></funcdef>
        <paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>
        <paramdef>lwres_buffer_t *<parameter>b</parameter></paramdef>
        <paramdef>lwres_lwpacket_t *<parameter>pkt</parameter></paramdef>
        <paramdef>lwres_gnbaresponse_t **<parameter>structp</parameter></paramdef>
        </funcprototype>

<funcprototype>
        <funcdef>
void
<function>lwres_gnbaresponse_free</function>
</funcdef>
        <paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>
        <paramdef>lwres_gnbaresponse_t **<parameter>structp</parameter></paramdef>
        </funcprototype>
<funcprototype>
        <funcdef>
void
<function>lwres_gnbarequest_free</function></funcdef>
        <paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>
        <paramdef>lwres_gnbarequest_t **<parameter>structp</parameter></paramdef>
      </funcprototype>
</funcsynopsis>

  </refsynopsisdiv>

  <refsect1>
    <title>DESCRIPTION</title>
    <para>
      These are low-level routines for creating and parsing
      lightweight resolver address-to-name lookup request and
      response messages.
    </para>
    <para>
      There are four main functions for the getnamebyaddr opcode.
      One render function converts a getnamebyaddr request structure &mdash;
      <type>lwres_gnbarequest_t</type> &mdash;
      to the lightweight resolver's canonical format.
      It is complemented by a parse function that converts a packet in this
      canonical format to a getnamebyaddr request structure.
      Another render function converts the getnamebyaddr response structure
      &mdash;
      <type>lwres_gnbaresponse_t</type>
      to the canonical format.
      This is complemented by a parse function which converts a packet in
      canonical format to a getnamebyaddr response structure.
    </para>
    <para>
      These structures are defined in
      <filename>lwres/lwres.h</filename>.
      They are shown below.
    </para>
    <para><programlisting>
#define LWRES_OPCODE_GETNAMEBYADDR      0x00010002U
</programlisting>
    </para>
    <para><programlisting>
typedef struct {
        lwres_uint32_t  flags;
        lwres_addr_t    addr;
} lwres_gnbarequest_t;
</programlisting>
    </para>
    <para><programlisting>
typedef struct {
        lwres_uint32_t  flags;
        lwres_uint16_t  naliases;
        char           *realname;
        char          **aliases;
        lwres_uint16_t  realnamelen;
        lwres_uint16_t *aliaslen;
        void           *base;
        size_t          baselen;
} lwres_gnbaresponse_t;
</programlisting>
    </para>

    <para><function>lwres_gnbarequest_render()</function>
      uses resolver context <varname>ctx</varname> to convert
      getnamebyaddr request structure <varname>req</varname> to
      canonical format.  The packet header structure
      <varname>pkt</varname> is initialised and transferred to buffer
      <varname>b</varname>.  The contents of <varname>*req</varname>
      are then appended to the buffer in canonical format.
      <function>lwres_gnbaresponse_render()</function> performs the
      same task, except it converts a getnamebyaddr response structure
      <type>lwres_gnbaresponse_t</type> to the lightweight resolver's
      canonical format.
    </para>

    <para><function>lwres_gnbarequest_parse()</function>
      uses context <varname>ctx</varname> to convert the contents of
      packet <varname>pkt</varname> to a
      <type>lwres_gnbarequest_t</type> structure.  Buffer
      <varname>b</varname> provides space to be used for storing this
      structure.  When the function succeeds, the resulting
      <type>lwres_gnbarequest_t</type> is made available through
      <varname>*structp</varname>.
      <function>lwres_gnbaresponse_parse()</function> offers the same
      semantics as <function>lwres_gnbarequest_parse()</function>
      except it yields a <type>lwres_gnbaresponse_t</type> structure.
    </para>

    <para><function>lwres_gnbaresponse_free()</function>
      and <function>lwres_gnbarequest_free()</function> release the
      memory in resolver context <varname>ctx</varname> that was
      allocated to the <type>lwres_gnbaresponse_t</type> or
      <type>lwres_gnbarequest_t</type> structures referenced via
      <varname>structp</varname>.  Any memory associated with
      ancillary buffers and strings for those structures is also
      discarded.
    </para>
  </refsect1>

  <refsect1>
    <title>RETURN VALUES</title>
    <para>
      The getnamebyaddr opcode functions
      <function>lwres_gnbarequest_render()</function>,
      <function>lwres_gnbaresponse_render()</function>
      <function>lwres_gnbarequest_parse()</function>
      and
      <function>lwres_gnbaresponse_parse()</function>
      all return
      <errorcode>LWRES_R_SUCCESS</errorcode>
      on success.
      They return
      <errorcode>LWRES_R_NOMEMORY</errorcode>
      if memory allocation fails.
      <errorcode>LWRES_R_UNEXPECTEDEND</errorcode>
      is returned if the available space in the buffer
      <varname>b</varname>
      is too small to accommodate the packet header or the
      <type>lwres_gnbarequest_t</type>
      and
      <type>lwres_gnbaresponse_t</type>
      structures.
      <function>lwres_gnbarequest_parse()</function>
      and
      <function>lwres_gnbaresponse_parse()</function>
      will return
      <errorcode>LWRES_R_UNEXPECTEDEND</errorcode>
      if the buffer is not empty after decoding the received packet.
      These functions will return
      <errorcode>LWRES_R_FAILURE</errorcode>
      if
      <structfield>pktflags</structfield>
      in the packet header structure
      <type>lwres_lwpacket_t</type>
      indicate that the packet is not a response to an earlier query.
    </para>
  </refsect1>
  <refsect1>
    <title>SEE ALSO</title>
    <para><citerefentry>
        <refentrytitle>lwres_packet</refentrytitle><manvolnum>3</manvolnum>
      </citerefentry>.
    </para>
  </refsect1>
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